The invention is in the field of apparatus for heating material by electron beam bombardment, such as a vapor source for depositing coating material on a substrate.
Electron-beam heated vapor sources are frequently used in vacuum coating systems. One such vapor source is described in U.S. Pat. No. 3,710,072, issued to Robert L. Shrader and Kazumi N. Tsujimoto and assigned to the assignee of the present invention. This vapor source comprised a single crucible, a single electron-beam gun, and a magnetic means for deflecting the electron beam through an arcuate path from the electron-beam gun to the crucible. The magnetic deflecting means included two parallel plates of magnetic material which were positioned on opposite sides of the electron-beam gun and extended on opposite sides of the crucible. The plates were polarized by interconnecting them with a single magnet near their ends which were further from the electron-beam gun. The magnet and the two pole pieces were part of a single magnetic circuit. The electron beam was deflected by the magnetic field produced between the pole pieces. This prior vapor source also included a means for sweeping the electron beam across the crucible.
In some applications it is desirable to install two or more vapor sources near each other in order to allow simultaneous evaporation of a plurality of materials from separate crucibles bombarded by separate electron beams. It is sometimes imperative that such crucibles be clustered whereby the vapors appear to come from a single direction. With many prior vapor source assemblies the close approach of side-by-side vapor sources was prevented by the pole pieces which extended on opposite sides of each crucible. Further, in order to prevent undesirable interactions between the magnetic fields of the separate vapor sources, it was sometimes necessary to place a magnetic shield to isolate the separate magnetic circuits of the separate vapor sources.